Refactor split and splice implementations.

Currently, the implementations of the split and splice operation are both
hidden behind the Bazel API implementation. This was sufficient to implement
splitting at the server and splicing at the client. In order to support the
other direction of splitting at the client and splicing at the server while
reusing their implementations, the code needs to be refactored. First, the
functionality of split and splice are explicitly exposed at the general
execution API interface and implemented in the sub APIs. Second, the
implementations of split and splice are factored into a separate utils class.

1 files changed, 155 insertions, 0 deletions

diff --git a/src/buildtool/execution_api/execution_service/cas_utils.cpp b/src/buildtool/execution_api/execution_service/cas_utils.cpp
new file mode 100644
index 00000000..3da56e28
--- /dev/null
+++ b/src/buildtool/execution_api/execution_service/cas_utils.cpp
@@ -0,0 +1,155 @@
+// Copyright 2024 Huawei Cloud Computing Technology Co., Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "src/buildtool/execution_api/execution_service/cas_utils.hpp"
+
+#include <fstream>
+
+#include "fmt/core.h"
+#include "src/buildtool/common/artifact_digest.hpp"
+#include "src/buildtool/compatibility/native_support.hpp"
+#include "src/buildtool/execution_api/execution_service/file_chunker.hpp"
+#include "src/buildtool/file_system/file_system_manager.hpp"
+#include "src/buildtool/file_system/git_repo.hpp"
+#include "src/buildtool/file_system/object_type.hpp"
+#include "src/buildtool/storage/fs_utils.hpp"
+#include "src/utils/cpp/hex_string.hpp"
+
+auto CASUtils::EnsureTreeInvariant(std::string const& data,
+                                   std::string const& hash,
+                                   Storage const& storage) noexcept
+    -> std::optional<std::string> {
+    auto entries = GitRepo::ReadTreeData(
+        data,
+        NativeSupport::Unprefix(hash),
+        [](auto const& /*unused*/) { return true; },
+        /*is_hex_id=*/true);
+    if (not entries) {
+        return fmt::format("could not read tree data {}", hash);
+    }
+    for (auto const& entry : *entries) {
+        for (auto const& item : entry.second) {
+            auto digest = static_cast<bazel_re::Digest>(
+                ArtifactDigest{ToHexString(entry.first),
+                               /*size is unknown*/ 0,
+                               IsTreeObject(item.type)});
+            if (not(IsTreeObject(item.type)
+                        ? storage.CAS().TreePath(digest)
+                        : storage.CAS().BlobPath(digest, false))) {
+                return fmt::format(
+                    "tree invariant violated {}: missing element {}",
+                    hash,
+                    digest.hash());
+            }
+            // The GitRepo::tree_entries_t data structure maps the object id to
+            // a list of entries of that object in possibly multiple trees. It
+            // is sufficient to check the existence of only one of these entries
+            // to be sure that the object is in CAS since they all have the same
+            // content.
+            break;
+        }
+    }
+    return std::nullopt;
+}
+
+auto CASUtils::SplitBlob(bazel_re::Digest const& blob_digest,
+                         Storage const& storage) noexcept
+    -> std::variant<std::vector<bazel_re::Digest>, grpc::Status> {
+
+    // Check blob existence.
+    auto path = NativeSupport::IsTree(blob_digest.hash())
+                    ? storage.CAS().TreePath(blob_digest)
+                    : storage.CAS().BlobPath(blob_digest, false);
+    if (not path) {
+        return grpc::Status{
+            grpc::StatusCode::NOT_FOUND,
+            fmt::format("blob not found {}", blob_digest.hash())};
+    }
+
+    // Split blob into chunks, store each chunk in CAS, and collect chunk
+    // digests.
+    auto chunker = FileChunker{*path};
+    if (not chunker.IsOpen()) {
+        return grpc::Status{
+            grpc::StatusCode::INTERNAL,
+            fmt::format("could not open blob {}", blob_digest.hash())};
+    }
+    auto chunk_digests = std::vector<bazel_re::Digest>{};
+    while (auto chunk = chunker.NextChunk()) {
+        auto chunk_digest = storage.CAS().StoreBlob(*chunk, false);
+        if (not chunk_digest) {
+            return grpc::Status{grpc::StatusCode::INTERNAL,
+                                fmt::format("could not store chunk of blob {}",
+                                            blob_digest.hash())};
+        }
+        chunk_digests.emplace_back(*chunk_digest);
+    }
+    if (not chunker.Finished()) {
+        return grpc::Status{
+            grpc::StatusCode::INTERNAL,
+            fmt::format("could not split blob {}", blob_digest.hash())};
+    }
+
+    return chunk_digests;
+}
+
+auto CASUtils::SpliceBlob(bazel_re::Digest const& blob_digest,
+                          std::vector<bazel_re::Digest> const& chunk_digests,
+                          Storage const& storage) noexcept
+    -> std::variant<bazel_re::Digest, grpc::Status> {
+
+    // Assemble blob from chunks.
+    auto tmp_dir = StorageUtils::CreateTypedTmpDir("splice");
+    auto tmp_file = tmp_dir->GetPath() / "blob";
+    {
+        std::ofstream tmp(tmp_file, std::ios::binary);
+        for (auto const& chunk_digest : chunk_digests) {
+            // Check chunk existence (only check file CAS).
+            auto path = storage.CAS().BlobPath(chunk_digest, false);
+            if (not path) {
+                return grpc::Status{
+                    grpc::StatusCode::NOT_FOUND,
+                    fmt::format("chunk not found {}", chunk_digest.hash())};
+            }
+            // Load chunk data.
+            auto chunk_data = FileSystemManager::ReadFile(*path);
+            if (not chunk_data) {
+                return grpc::Status{grpc::StatusCode::INTERNAL,
+                                    fmt::format("could read chunk data {}",
+                                                chunk_digest.hash())};
+            }
+            tmp << *chunk_data;
+        }
+    }
+
+    // Store resulting blob in according CAS.
+    auto const& hash = blob_digest.hash();
+    if (NativeSupport::IsTree(hash)) {
+        auto const& digest =
+            storage.CAS().StoreTree</* kOwner= */ true>(tmp_file);
+        if (not digest) {
+            return grpc::Status{grpc::StatusCode::INTERNAL,
+                                fmt::format("could not store tree {}", hash)};
+        }
+        return *digest;
+    }
+
+    auto const& digest =
+        storage.CAS().StoreBlob</* kOwner= */ true>(tmp_file, false);
+    if (not digest) {
+        return grpc::Status{grpc::StatusCode::INTERNAL,
+                            fmt::format("could not store blob {}", hash)};
+    }
+    return *digest;
+}